It is proposed that a research effort be continued to determine the nucleation properties of respirable coal dust and to study ways of enhancing the nucleation process. Nucleation efficiencies for coal dust particles in the size range 0.01 micron to 10 micron will be measured as a function of size, composition, electric charge, and the environmental factors, temperature, pressure, and humidity. The measurements will be made in real time in a specially designed thermal diffusion cloud chamber, which provides for the simultaneous control of all environmental factors and residence time. Scavenging techniques designed to improve the nucleation efficiencies will be studied and evaluated. The results of this research are important in the control of respirable dust in coal mines and in understanding the behavior and deposition of coal dust particles in the moist environment of the human lung. BIBLIOGRAPHIC REFERENCES: "The Control of Coal Dust and its Relationship to Coal Workers' Pneumoconiosis," J.T. Brown and F.D. Schowengerdt, Proceedings of the Institute on Coal Mine Health and Safety, CSM, 1975. "Colorado School of Mines Tackles Control of Respirable Coal Dust," F.D. Schowengerdt and J.T. Brown, Coal Age 81, 129, 1976.